Low friction fabric-lined bearings and improved fabric therefor

ABSTRACT

Unblended yarns are constructed and woven with other yarns to form a mixed fabric which is particularly suitable for use as the liner for resin bodied annular bearings which are subject to reversing loads, that is where one bearing element oscillates relative to the other or relative rotation or movement of the bearing elements regularly reverses in direction. More particularly, yarn of Teflon filaments and yarn of bondable filaments are woven in a 1 X 1 plain weave so that the filaments are just sufficiently loose to allow the capillary action of the liquid resin to thoroughly impregnate the fabric in the manufacture of the bearing and anchor the Teflon filaments to prevent their being worked loose from the resin by the reversing loads.

United States Patent [1 1 Butzow et al.

[ LOW FRICTION FABRIC-LINED BEARINGS AND IMPROVED FABRIC THEREFOR [75]Inventors: Neil W. Butzow, Greendale;

Bernard Harris, Bayside, both of Wis.

[73] Assignee: Rexnord Inc., Milwaukee, Wis.

[22] Filed: Dec. 21, 1972 21 Appl. No.: 317,210

[52] US. Cl 308/238, 139/420 A, 161/91 [451 Apr. 16, 1974 Rasero 308/238Primary Examiner-Charles J. Mylhre Assistant Examiner-Barry Grossman 57] ABSTRACT Unblended yarns are constructed and woven with other yarnsto form a mixed fabric which is particularly suitable for use as theliner for resin bodied annular bearings which are subject to reversingloads, that is where one bearing element oscillates relative to theother or relative rotation or movement of the bearing elements regularlyreverses in direction. More particularly, yarn of Teflon filaments andyarn of bondable filaments are woven in a 1 X 1 plain weave so that thefilaments are just sufficiently loose to allow the capillary action ofthe liquid resin to thoroughly impregnate the fabric in the manufactureof the bearing and anchor the Teflon filaments to prevent their beingworked loose from the resin by the reversing loads.

7 Claims, 6 Drawing Figures LOW FRICTION FABRIC-LINED BEARINGS ANDIMPROVED FABRIC THEREFOR CROSS REFERENCE TO RELATED APPLICATION Thebearing disclosed and claimed in the copending application filed Dec. 4,1970 by the present inventors, Ser. No. 95,363 and entitled SeamlessFabric Lined Bearing of Multiple Length Construction is particularlyintended for use with the fabric of the present invention. The method ofmaking the bearing is thesubject of us. Pat No. 3,616,000. I

BACKGROUND OF THE INVENTION 1. Field of Invention The present inventioninvolves the selection of the fiber content of the yarns, the countsandpicks of the warp and filler and weaving specifications for a fabric foruse as the liner of a low friction bearing. The fabric of the presentinvention is adapted for use for example in the construction of bearingsin accordance with the disclosure of U.S. Pat. No. 3,616,000 of thepresent inventors.

2. Description of the Prior Art For some time a number of polymers havebeen available for use as a low friction bearing liner in the form of afabric of woven monofilament yarns. British Pat.

No. 698,611 published Oct. 21, 1953 describes improvements inanti-friction materials including the use of filaments of polyethylenemade on an extruding machine and cold-stretched if desired. Each yarn isdoubled with a textile yarn and woven into a fabric, impregnated withresin, and moulded under heat and pressure to a structure of one or moreplies.

A polytetraflouroethylene resin, presently marketed under the trademarkTeflon, is a more recently developed polymer of outstanding low-frictioncharacteristics. According to the disclosure of U.S. Pat. No. 2,885,248,Teflon threads are interwoven into a cloth and this cloth is resinimpregnated and located in the resin body so that substantially all ofthe threads forming the front face of the Teflon cloth are exposed toform the face of the bearing and the entire rear side of the cloth isembedded in the resin. However, this fabric is unsuitable becausethermosetting resins are incapable of bonding to Teflon.

Subsequently, Teflon cords or threads'were woven with bondable cords orthreads such that the face of the cloth to be exposed comprisedsubstantially all Teflon material and the face to be bonded comprisedsubstantially all bondable material. U.S. Reissue Pat. No.

24,765 shows such a compound fabric having a threefloat twill weave. Thepatent suggests also that a satin weave might be used.

Bearings of especially high quality in terms of load capacity, lowbreak-away torque, and wear resistance can be made using such a compoundfabric. However, such bearings are serviceable only under relativelyclean conditions and with an especially well-finished steel matingelement. Any slight imperfection in the surface of the mating element orany intruded sand or grit particles will quickly snag a Teflon filamentand pull the cord or thread from the face of the bearing and as a resultdestroy the bearing. It has also been found that reversing movementsnormal to the filaments particularly accelerate the wear and failure ofthe bearing. This is because in providing a compound fabric of suchThese floats tend to be more readily broken away from the backing byimperfections or foreign particles in the bearing. While this tendencyis reduced in a fabric ofa plain or 1X 1 weave, a bearing with a plainfabric of whatever proportion of Teflon might be selected, generallyappears comparatively secure but fails quickly due to overheatingbecause oftoo little Teflon on the bearing face or appears to be acomparatively good bearing but fails quickly due to loosening of thefabric because of inadequeate bonding of the reverse side. Thesemutually exclusive considerations of course, led to the development ofthe compound fabric some years ago.

The present invention is based upon the discovery in a bearing ofacertain manufacture that a plain fabric of Teflon and bondable yarns ofcertain relative dimensions can provide a bearing comparable to or.better than a bearing having the compound fabric referred to. It isbelieved that the improvement is the result of 1) reducing the amount ofthe bondable yarns which reach to the bearing face and '2) assuringadequate looseness of the bondable filaments so that the entire fabricis assuredly filled with resin in the manufacture of the bearing. 7

In the type of bearing to which the present invention appears limited,the fabric is woven in the form of a sleeve having longitudinal Teflonwarp yarns and circumferential filling yarns of such as Dacron and isheld against a mandrel by the tension ofthe filling yarns uponheat-shrinking such that at spaced points the filling yarns extendbetween alternate warp yarns and the resin-mandrel face of the bearing.According to the present invention the relativesizes and spacing of thewarp and filling yarns are selected so that between said spaced pointsthe filling yarns bridge the alternate warp yarns and support themselvessome distance from the resin-mandrel face of the bearing.

Any suitable material for the filaments of the filling yarn might beemployed. Dacron is the trademark used for a commercially availablepolyester of a dihydric alcohol and terephthalic acid. This material isheatshrinkable and is especially suitable for use as the filaments ofthe bondable yarns of the fabric of the present invention.

The commercial availability of the Teflon and Dacron yarns should benoted because the Teflon yarns in particular are not to be doubled ortripled. Doubling is mentioned in the British Pat. No. 698,61 1, abovenoted and must be avoided in carrying out the present invention becausedoubled or tripled yarns cannot be consis tently pressed against themandrel to form the bearing face.

At present, Teflon yarns of 30, 60 and filaments each are available.Such yarns of unbleached Teflon have Deniers of 200, 400 and 1200*respectively. While these specifications are arbitary, they indicatethat the Teflon monomer has an optimum filament diameter which wasarrived at empirically and is now standardized.

The fabric of the present invention utilizes the 400 Denier, 60 filamentTeflon yarn because the other two available selections are respectivelytoo fine and too coarse. According to the explanation of the inventionwhich is offered, the finer yarn would be preferable, but are too finefor available looms for weaving seam- A wider selection of Dacron yarnsis available and the selection of the filling yarn size is made withreference to the size of the 60 filament, 400 Denier unbleached Teflonwarp yarn which essentially here, is the only choice available.

The twist of any woven yarn is generally required to some degree forhandling of the yarns in weaving. In the fabric of the present inventiona minimum of twist is desired because, in general, twisting increasesthe resistance of the yarns to the crimping which is required of therelatively much stiffer Teflon yarns and, twisting in effect bundles theDacron filaments too tightly and prevents entry of the liquid resin intothe interstices of the yarns as is required for bonding of these yarns.

Notwithstanding the desireability of unplied Teflon yarns with a minimumof twist, one difficulty in weaving must be noted and which, so far hasrequired blending the warp yarn with about percent of filaments of otherthan Teflon so that the tension of the warp yarns can be maintained.This tension is maintained by drawing the yarns over a number of pegsand the 5 percent blended yarn need not be of a bondable material. Infact, filaments of polyethylene is recommended and preferred. Thismaterial is lubricious and non-bondable as was indicated by BritishPat.- No. 698,611 but provides the desired tensioning effect in weaving.A polypropylene is also recommended.

SUMMARY OF THE INVENTION The fabric of the present invention is intendedfor providing the Teflon face of a hardened resin backing which is toform one part of a low-friction bearing. The fabric is of a plain l X lweave for durability and comprises Teflon warp yarns and bondable orDacron filling yarns of such size and number which are selected so thatrather than providing as great an area of Teflon at the bearing surfaceas possible, the maximum practicable number of relatively much smallerareas of Teflon are provided. The fabric is still adequately bond ableon either side, or possibly more so, depending upon the comparison; thesynergistic effect in providing many small Teflon areas is a bearing ofuniquely high capacity and durability for this type of fabric and isbelieved to be associated with the slight tendency for some of theTeflon molecules to be rubbed off from the filaments and over theadjoining non-Teflon surfaces. By reducing the size of the Teflon areasand effecting a corresponding increase in their number, the distanceacross the non-Teflon areas is thus reduced and maximum utilization ofthe rubbed-off Teflon is believed to provide the improvement noted.While this conjecture has not yet been verified, it seems to bejustified by actual tests of bearings with several different fabricshaving only slightly larger and fewer areas. The warp comprisescommercially available unbleached Teflon yarns of 400 Denier having aminimum of twist allowing maximum crimping, thewarp end count being inthe order of 85 and thus relatively near the maximum allowed with suchyarns and such that the filling yarns are allowed a minimum of crimp.The filling yarns are of Dacron and of about a 200 Denier such that thecrosssection of each yarn is about two-thirds that of each Teflon warpyarn, the filling pick count being about 56 and thus also abouttwo-thirds that of the end count.

DESCRIPTION OF VIEWS OF THE DRAWING FIG. 1 shows in section a typicalbearing using the fabric as the lining for the outer glass-reinforcedresin body in which the inner member turns.

FIG. 2 is greatly enlarged plan view of the fabric of the presentinvention for the bearing of FIG. 1.

FIG. 3 is a similarly enlarged section of the bearing showing one of theTeflon yarns in elevation.

FIG. 4 is a similarly enlarged cross-section of the bearing showing aportion of the Dacron filling yarn in elevation.

FIGS. 5 and 6 are representations of larger and smaller areas of theTeflon at the bearing surface with arrow indicating the Teflon which isrubbed onto the intermediate adjacent areas.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cylinder 11 shown in FIG. 1represents both the mandrel on which the bearing 12 is made and theshaft which is tumable relative to bearing 12. As described in therelated application referred to, bearing 12 is manufactured in multipleas a long tube which is cut to the desired lengths of the individualbearings. The face I of bearing 12 is formed by the seamless fabricsleeve 13 which is first heat-shrunk on the mandrel (l1) and is thenspirally wrapped with a resin-carrying tape of parallel roves of glassfilaments 14. The resin is then cured to form the resin body 15 ofbearing 12.

Sleeve 13 includes the longitudinal warp yarns 16 which are comprised ofTeflon filaments having a nominal twist. Because the fabric is of aplain l X l weave and in the form of a seamless sleeve, thecircumferential filling is comprised of a single yarn 17 which extendsin a spiral or circumferentially and from one end to the other end ofthe bearing face. Yarn 17 is of a size or number of filaments which iscritical to carrying out the present invention. The filaments of yarn 17are of Dacron which shrinks upon heating and also provides strength andbonding.

FIGS. 2-4 show a section of fabric sleeve 13 enlarged about times andare believed to illustrate the physical characteristics of the fabricwhich provide the unexpected results observed in testing bearings ofidentical manufacture with similar fabric sleeves but merely differentyarn sizes and spacing.

As shown, the filling yarn 17 is about twothirds the size of the warpyarns 16; the warp yarns 16 are closely spaced and sharply cn'mped overand under the parallel well-spaced turns of the filling yarn 17 whichhas practically no crimp; a part of each crimp of the warp yarns 16 ispressed against the mandrel (11) by the heatshrunk circumferentialfilling yarn 17 which bridges the warp yarns so that the filling yarnpositively spaced from the bearing face; the warp yarns 16 are flattenedagainst mandrel (11) to form a large number of Teflon bearing areas in auniform, closely spaced pattern.

FIGS. 5 and 6 represent the larger. and smaller patterns which wereprovided by several of the tested fabrics. The larger pattern showsrelatively larger squares of Teflon with larger intermediate resin areasalthough both patterns include the same overall'percentage of Teflon andintermediate areas of resin.As is known, some amount of Teflon is rubbedby the moving hearing part (11) from the Teflon areas and over theajoining portions of the resin areas. However, in the smaller patternthis effect provides a significantly greater total area of Teflon and asignificantly improved bearing wear life. That is, with the greater areaof Teflon, both the enlargement of the bearing and the deterioration ofthe bearing due to wear and overheating is reduced so that a bearing ofsubstantially greater load capacity and wear life is provided.

The exact specifications of the fabric shown and described are:

Warp: 87 ends per inch; 400 denier unbleached Teflon yarns of 60filaments with the producers twist; each yarn may include somepolypropylene filaments for tensioning in weaving. Filling 56 ends perinch; 220 denier type 52 Dacron yarns of 50 filaments with Z twist of 5per inch. Another aspect of the invention respects the side of thefabric over which the glass filaments are wound.

Also as shown in FIGS. 24, the warp yarns 16 protrude beyond the fillingyarn 17 but are not flattened as on the bearing side of the fabric andsignificant depressions appear where each two adjoining warp yarns l6.cross each other. The first layer of glass filaments 14 which arespirally wound over sleeve 13 include a significant number which lie inthese depressions so that the fabric is especially well anchored by theglass filaments 14 as well as by the resin body 15.

We claim:

1. In a low-friction bearing having a filament reinforced thermosetresin body and a fabric having one face embedded therein and the otherface substantially exposed to form the bearing surface, the improvedfabric which comprises warp and filling yarns woven with a 1 X 1 weave,the warp yarns comprising Teflon filaments and having a denier in theorder of 400, the filling yarns comprising bondable filaments such asDacron and having a denier in the order of 200, said fabric having inthe order of 90 end and 60 pick counts, all of said yarns having a twistof no more than one per inch, the area of each face of said fabric beingin the order of 55 to 60 percent Teflon to provide on either selectedside a durable bearing surface, 40 to 45 percent of the remaining areaof each side comprising said bondable filaments which are adequatelyspaced to and interlocked by the intersticial resin. i

2. A fabric sleeve for shrinking over a mandrel and embedding in ahardenable material to form the hearing face of a low-friction device,said fabric being of a l X 1 weave and comprising between 80 and 90 endsand between 50 and 60 picks per inch, each warp yarn being of Teflonfilaments with minimum twist in the order of 400 denier and each fillingyarn being of Dacron filaments and in the order of 200 denier.

3. In a journal bearing which comprises a thermoset resin body havingwound filaments for internal reinforcing and a fabric embedded thereinat and to form the bearing face, said fabric being of a 1 X l weave andwoven in the form of a sleeve and having longitudinal warp yarns oflow-friction filaments of a material such as Teflon and acircumferential filling yarn of filaments of a heat-shrinkable andbondable material such as Dacron, the cross-section and spacing of saidfilling yarns being about two-thirds that of the warp yarns whereby thefilling yarns are substantially uncrimped and the warp yarns forming thebearing face appear as ros of relatively small squares of nominalspacing.

4. In a journal bearing which comprises a thermoset resin body havingwound filaments for internal reinforcing and a fabric embedded thereinat and to form the bearing face, said fabric being of a l X l weave andwoven in the form of a sleeve and having longitudinal warp yarns oflow-friction filaments of a material such as Teflon and circumferentialfilling yarns of filaments of a heat-shrinkable and bondable materialsuch as Dacron, said bearing of the type wherein the fabric is heldagainst a mandrel by the tension of the filling yarns uponheat-shrinking such that at spaced points the filling yarns cross-overand press alternate warp yarns against the mandrel and at intermediatepoints the filling yarns extend between alternate warp yarns and theresin-mandrel face of the bearing, the relative sizes and spacing of thewarp and filling yarns being such that between said spaced points thefilling yarns bridge the alternate warp yarns and support themselvessome distance from the resin-mandrel face of the bearing.

5. The bearing of claim 3 which is in the form of a cylinder and whereinthe Teflon yarns on the other face of the fabric form similar rows ofdiagonally arranged projections and the reinforcing filaments are woundin a spiralso that a significant number of said filaments lie betweensuch projections to firmly anchor the fabric in the resin body of thebearing.

6. The bearing of claim 4 which is in the form of a cylinder and whereinthe warp yarn forming the other face of the fabric includes projectionswhich are spaced axially and circumferentially on parallel diagonallines and the internal reinforcing filaments are wound in a spiral sothat a significant number of said filaments lie between such projectionsto firmly anchor the fabric in the resin body of the bearing.

7. In a journal bearing which comprises a reinforced thermoset resinbody and a fabric embedded therein at and to form the bearing face, saidfabric being woven with a l X l weave and having longitudinal warp yarnsof low-friction filaments of, a material such as Teflon and acircumferential filling yarn of filaments of a bondable material such asDacron, the cross-section and spacing of said filling yarns being abouttwo-thirds that of the warp yarns whereby the filling yarns aresubstantially uncrimped and the warp yarns forming the bearing faceappear as rows of relatively small squares of nominal spacing.

2. A fabric sleeve for shrinking over a mandrel and embedding in ahardenable material to form the bearing face of a low-friction device,said fabric being of a 1 X 1 weave and comprising between 80 and 90 endsand between 50 and 60 picks per inch, each warp yarn being of Teflonfilaments with minimum twist in the order of 400 denier and each fillingyarn being of Dacron filaments and in the order of 200 denier.
 3. In ajournal bearing which comprises a thermoset resin body having woundfilaments for internal reinforcing and a fabric embedded therein at andto form the bearing face, said fabric being of a 1 X 1 weave and wovenin the form of a sleeve and having longitudinal warp yarns oflow-friction filaments of a material such as Teflon and acircumferential filling yarn of filaments of a heat-shrinkable andbondable material such as Dacron, the cross-section and spacing of saidfilling yarns being about two-thirds that of the warp yarns whereby thefilling yarns are substantially uncrimped and the warp yarns forming thebearing face appear as ros of relatively small squares of nominalspacing.
 4. In a journal bearing which comprises a thermoset resin bodyhaving wound filaments for internal reinforcing and a fabric embeddedtherein at and to form the bearing face, said fabric being of a 1 X 1weave and woven in the form of a sleeve and having longitudinal warpyarns of low-friction filaments of a material such as Teflon andcircumferential filling yarns of filaments of a heat-shrinkable andbondable material such as Dacron, said bearing of the type wherein thefabric is held against a mandrel by the tension of the filling yarnsupon heat-shrinking such that at spaced points the filling yarnscross-over and press alternate warp yarns against the mandrel and atintermediate points the filling yarns extend between alternate warpyarns and the resin-mandrel face of the bearing, the relative sizes andspacing of the warp and filling yarns being such that between saidspaced points the filling yarns bridge the alternate warp yarns aNdsupport themselves some distance from the resin-mandrel face of thebearing.
 5. The bearing of claim 3 which is in the form of a cylinderand wherein the Teflon yarns on the other face of the fabric formsimilar rows of diagonally arranged projections and the reinforcingfilaments are wound in a spiral so that a significant number of saidfilaments lie between such projections to firmly anchor the fabric inthe resin body of the bearing.
 6. The bearing of claim 4 which is in theform of a cylinder and wherein the warp yarn forming the other face ofthe fabric includes projections which are spaced axially andcircumferentially on parallel diagonal lines and the internalreinforcing filaments are wound in a spiral so that a significant numberof said filaments lie between such projections to firmly anchor thefabric in the resin body of the bearing.
 7. In a journal bearing whichcomprises a reinforced thermoset resin body and a fabric embeddedtherein at and to form the bearing face, said fabric being woven with a1 X 1 weave and having longitudinal warp yarns of low-friction filamentsof a material such as Teflon and a circumferential filling yarn offilaments of a bondable material such as Dacron, the cross-section andspacing of said filling yarns being about two-thirds that of the warpyarns whereby the filling yarns are substantially uncrimped and the warpyarns forming the bearing face appear as rows of relatively smallsquares of nominal spacing.